Answer to the Parasite Case of the Week 716: Cyclospora cayetanensis oocysts
On the wet mount preparation with Lugol's iodine, one can nicely appreciate the spherical oocyst with well-defined outer wall and internal globular bodies. The oocysts are not highlighted by the Heine and trichrome stains (latter not shown), but their presence may be suspected by their negative contour. Confirmation can be made by staining with modified acid fast stain (or modified safranin stain), and by demonstrating autofluorescence with fluorescence microscopy.
It is important to measure the oocysts on the stains above, since cryptosporidium oocysts have a similar appearance. C. cayetanensis oocysts are 8-10 micrometers in diameter, while Cryptosporidium spp. oocysts are 4-5.